Advanced Materials Research Vols. 550-553

Abstract: An intumescent flame retardant (IFR) system containing phosphorus-silicon (EMPZR) and ammonium polyphosphate (APP) was used to improve the flame retardancy of poly(ethylene-co-vinyl acetate)(EVA). The influence of EMPZR contents on the flame retardance of EVA/EMPZR/APP composites has been studied. It was found that the reasonable mass ratio of EMPZR/APP in EVA/EMPZR/APP composites is 20/20, whose limiting oxygen index (LOI) value was improved from 19.0 for EVA to 28.6, and the burning grading reached to UL-94 V-0. The thermal behavior of EVA and IFR-EVA was investigated by dynamic thermo gravimetric analysis (TGA) at different heating rates and then the thermal degradation activation energies of EVA and IFR-EVA were determined by using Flynn-Wall-Ozawa method. Meanwhile, morphology of the char residue obtained from burning IFR-EVA in LOI test was studied through the scanning electron microscopy SEM observation, the rich compact char layer in which could explain the good flame retardance and the synergistic effect between EMPZR and APP.

Abstract: Due to high in desulfurization activity, big in sulfur capacity and easy in regeneration, iron oxide desulfurization sorbents have been used to remove hydrogen sulfide derived from coal gas at normal temperature. At the same time the removing H₂S from coal gas containing CO can generate COS, which is more difficult to removal than H₂S. γ-FeOOH desulfurization sorbent was prepared by the fast oxidizing method. Kinetics study of COS formation in γ-FeOOH desulfurization was performed under 40-80°C，the CO+H₂S+N₂ mixtures and over a residence time of 0.04~0.09s. LevenbergMarquardt and lsqcurvefit methods in MATLAB are used for the regression of experimental data. The established kinetics model of COS formation is described by the following: r_COS=8.9990*10⁴exp(-22540/RT)P_COP_H2S. The recognition of mechanism model reveals that Langmuir-Hinshelwood mechanism can perfectly fit with this reaction system.

Abstract: In order to study the thermites systematically, six different thermites were chosen and prepared, then the thermodynamic properties were measured. It was found that Mg+MnO₂, Al+Fe₃O₄ and Mg+CuO combusted steadily and slowly, while Mg+MnO₂ had a high combustion temperature; Mg+CuO, Mg+Fe₃O₄ and Mg+MnO₂ had lower starting reaction temperature, higher releasing heat, and reacted easily; Mg+MnO₂, Mg+CuO and Al+CuO had higher combustion heat and complete combustion capacity. Mg+MnO₂ and Mg+CuO are two ideal thermites, have bright practical application prospect.

Abstract: This study demonstrates the thermal actions of tert-butyl peroxybenzoate (TBPB) which is widely used in the plastic and rubber industries. The thermodynamic and kinetic analysis were performed on the basis of dynamic and adiabatic calorimetric applications which had been accepted as good assistants for investigating materials’ thermal decomposition. In essence, TBPB is reactive and exothermically unstable. Differential scanning calorimetry (DSC) and accelerating rate calorimeter (ARC) were employed to supply basic data and safety index. Experiments were taken under different scanning rates as well as various sample mass. The temperature and pressure curves of TBPB during decomposition were recorded. Based on the significant parameters calculated, self-accelerating decomposition temperature (SADT) of TBPB worked out was 50°C.

Abstract: The combustion characteristics of decorative materials were studied by thermal analysis. The experiments were performed in three kind of oxygen concentration (7%, 14%, 21%), the heating rate were 15°C/min and 30°C/min respectively. The ignition point and maximum weight loss rated were analyzed. Based on the Coats-Redfern integral method, the results show that the combustion process were first order reaction.

Abstract: The paper introduced the basic performance and thermal insulation mechanism of a new building thermal insulation material—FHP-Vc inorganic composite silicate heat-insulating board which is used as the thermal insulation material for exterior wall. Based on the experiments and analysis of the heat transfer performance of FHP-Vc board, it has been found that the thermal performance of FHP-Vc board meets the current design standard of building energy efficiency. At the same time, it is a new building energy-saving material which has good insulation, non-burning, reliable and economical properties.

Abstract: The paper studied the change of the coal characteristics based on the influence of lignite naturally oxidated in air. The original lignite and lignite naturally oxidated under different time were analyzed by the FTIR technology. The reason that metamorphism of lignite was vulnerable by oxygen was analyzed from the side of coal molecular structure. It indicates that lignite of a low rank coal easily oxidated is mainly because lignite has more active groups in coal molecular such as methyl, methylene, hydroxyl, aromatic ether, oxygen button and ether key. In lignite molecular, side chains of aromatic ring structure unit is firstly oxidized. The bridge button or side chains of coal molecular structure unit are easily oxidized at the same time with the structure of the bridge between units fracturing oxidation. Number of aromatic hydrocarbons remains stable after oxidation. General trend of cycloparafin hydrocarbon as well as aliphatic hydrocarbon are gradually reduced over the oxidized time.

Abstract: The thermodynamics of acetic acid steam reforming (AASR) for hydrogen production were simulated using a Gibbs free energy minimization method to study the influences of pressure, temperature and water to acetic acid molar feed ratios (WAFR) on the AASR. On the basis of the equilibrium calculations, the optimal operating conditions obtained were 700-800 oC, 1bar and WAFR = 6-10. At these conditions, the yield and selectivity of hydrogen were maximized and the formation of methane and coke was almost inhibited. Higher pressures had negative effects on the yields and selectivities of hydrogen and carbon monoxide. With increasing temperature from 300 to 1000 oC, the selectivity for hydrogen and carbon monoxide increased significantly along with a reduction in methane selectivity. Increase in the WAFR led to the increase in hydrogen selectivity and the decrease in carbon monoxide selectivity.

Abstract: An investigation on electronic, elastic and thermodynamic properties of VN under high pressure has been conducted using first-principles calculations based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. At elevated pressures VN is predicted to undergo a structural phase transition from the relatively open NaCl-type structure into the denser CsCl-type atomic arrangement. The predicted transition pressure is 189 GPa. The elastic constants, Debye temperature as a function of pressure and temperature of VN are presented.

Abstract: Potential energy scan for U2 was performed by density functional theory (DFT) method at the B3LYP level in combination with the (ECP80MWB_AVQZ + 2f) basis set. The dissociation energy of U2, after being corrected for the zero-point vibrational energy, is 2.482 eV, which is in good agreement with the experiment. The calculated energy was fit to the typical potential functions of Morse, Lennard-Jones (L-J) and Rydberg. Both the Morse and Rydberg functions are good representatives of the potentials, but the Lennard-Jones function is not. The anharmonicity constant is very small. The anharmonic frequency is 113.99 cm^–1. Thermodynamic properties of entropy and heat capacity at 298.2 K – 1500 K were calculated by using DFT-B3LYP computational results and Morse parameters, respectively. The relationship between entropy and temperature was established.